Circuit interrupter



June 13, 1933.

R. C. MASON 1,914,143

CIRCUIT INTERRUPTER Filed Feb. 1, 1928 ig'g. 2. N41

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INVENTOR Far/'c C Maso/z ATTRNEY Patented June 13, 1933 UNITED STATES PATENT OFFICE 'i RURIC C. MASON, OF PRINCETON, NEW JERSEY, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA 'CIRCUIT INTERRUPTER i Application led February 1, 1928. Serial No. 251,064.

My invention relates to interrupting means for electric circuits and particularly to means for interrupting circuits of high voltages while supplying heavy loads. The general principles of my invention, however, are applicable in connection with devices for inter- Another object of my invention is the provision of means for interrupting electrical circuits by means of a pair of separable contacts operating. in air or other gaseous media without the need of resorting to the use of oil or similar means for quenching the arcs incident to separation of the contacts.

l@ther objects of my invention will be apparent upon reading the following specification in `connection with the drawing, in

which;

Figure l is a View, in front elevation, of a deionizing structure embodying my invention;

Fig. 2 is a side elevation of the structure shown in Fig. l;

Fig. 3 is a view, partly in section, of one of the elements embodied in the structure aforesaid, and

Fig. 4 is a sectional View taken along the line IV-IV of Fig. 2.

Where it has been necessary, in the prior art, to interrupt circuits of relatively high voltage or circuits carrying large currents, it has been the practice to open the circuit at a pair of separable contacts immersed in oil, or some other liquid medium. which has the property of quenching arcs incident to such interruption.

It has heretofore been necessary to employ containers for the liquid which were of considerable size and, therefore, expensive and the arc-quenching media usually employed were oils, the use of which involved a considerable tire hazard in case of accident.'

In Patent No. 1,836,994, issued Dec. 15. 1931, for Circuit interrupters, on an application tiled by Joseph Slepian and assigned to the Westinghouse Electric & Manufacturing Company, it is shown that, where electric arcs are compelled to operate in narrow channels or slots between walls of refractory insulating material, such walls have the property of strongl deionizing the arc path, and, therefore, of ultilling much the same. arcquenching function as the liquids of the prior art. Such a deionizing means is particularly effective in aiding the interruption of alternating currents by reason of the fact that, when the current in the arc passes through zero, in the course of the alternating current cycle, the contiguity of the refractory walls results in rapid destruction of all thel free ions which gave conductivity to the previously existing arc. When the alternating voltage across the terminals of the arc path rises, on the succeeding half of the alternating wave, the conductivity of the are path has fallen to such degree that the voltage is insufficient to re-establish current flow along the path, and the arc, therefore, remains extinct.

In accor-dance with my invention, the arc to be interrupted may be impelled to operate Within the narrow portion of a slot having refractory insulating walls, positioned immediately above a pair of separable contacts, and formed by suitably shaped blocks of laminated magnetic material having their opposing faces coated with layers of a suitable refractory insulating material. The magnetic reaction of this system is such as to draw the arc upward into theV narrow space between the insulated walls without the necessity of using a blowout magnet, such as is commonly used in many types of openair circuit breakers. In consequence, a very cheap, rugged and simple deionizing structure is provided.

With the foregoing objects and purposes in mind, reference may be had, for an untacts or the auxiliary arcing contacts of a circuit interrupter of conventional design. No detailed description of the latter will be given, since its precise structure does not concern this invention and since such circuit interrupters are well known in the art.

The deionizing structure embodying my invention comprises a pair of side plates 4 which may be of any suitable refractory insulating material, such as asbestos, and which are positioned on each side of the path of movement of the contact 3. The path of the arc incident to the separation of such contacts is, therefore, enclosed between the side walls 4 4.

The deionizing structure l consists of two units composed ofsuitable laminations of iron or other magnetic material having what may be termed a curved bevel at their upper and lower edges. The plane of the laminations is perpendicular to said edges and the laminations are separated into groups of l0 or so by sheets of insulating material. Preferably also, the surfaces of the'individual laminationsare provided with insulating coatings such as are familiar in connection with transformer-core laminations.

F ig. 3 is a View, partly in section, of one bundle of such laminations.

Two bundles of laminations, composed as just described, are supported with their curved faces toward each other, as shown in Fig. 4. They may be supported in position and the laminations held firmly in place by through-bolts 8 securing them to end plates 9.

The curved bevels on the laminations thus form a slot having a side mouth opening downwardly, between which the movable Contact 3 travels and draws an arc when the circuit interrupter opens. The adjacent faces of the laminations are covered by layers of some suitable refractory insulating material. One such material is a mixture of soapstone with suficient water-glass to form a binder. The edges of the laminations may be coated with this mixture and the same allowed to dry; and, if desired, baked to harden it.

The tapering groove in which the arc is first formed narrows to a narrow slot having parallel sides over almost the entire faces of the laminations.

By reason of well known magnetic reactions, a force is exerted on the are by the magnetic structure which draws it up into the narow slot. This movement of the arc is due to the fact that an arc adjacent to magnetic material is acted upon by electromagnetic forces which move it into such position that the reluctance of the path of the flux set up by the arc current is a minimum. Thus, when the arc is initially drawn between the contact members 2 and 3, the magnetic material above the are provides a path of lower reluctance for the flux above the arc than for the flux below the arc. This distortion of the flux set up by the are moves the arc upwardly until the reluctance of the portions of the fiux paths above and below the are are equal, when the are assumes a position of equilibrium. That is, the arc is moved into the slot until it reaches a point adjacent the center of the space between the magnetic plates, and there is then no force on the arc due to the flux surrounding the arc seeking a path of lower reluctance. If the arc should move past this point and toward the top of the magnetic plates, there will then be a force on the arc acting to move it back toward the center of the space between the magnetic plates.

As shown on the drawing, the laminations of magnetic material are shaped the same at the top and bottom and the groups are spaced apart uniformly with no connecting portions of magnetic material providing a low reluctance path so that the path of the are where the reluctance to its flux is a minimum is adjacent the center of the slot and the magnetic forces on the arc are in equilibrium. The iron laminations are of such width as to exten-d the whole length of the arc between the parallel arc horns 9. The arc is hence acted upon by uniform forces along its whole length and is moved to a central position in the slot where the magnetic forces on the are are in equilibrium duc to the symmetry of the magnetic members about an axis parallel to the arc path, until it is extinguished. T he arc is thus delinitely controlled within the slot where it may be effectively deionized and is prevented from being blown out of the slot and damaging adjacent apparatus.

The arc is extinguished by the deionizing effect of the walls which destroy the ions which remain in the arc path at the instant the alternating current passes through zero. Consequently, when the voltage across the separable contacts 2, 3 rises in the succeeding half cycle of alternating-current electrometive force, it is incapable of initiating a recurrence. of current flow across the arc path and, therefore, the arc remains extinct.

Where the current and voltage to be interrupted are small in magnitude, it is sufficient toleave the slot between the laminations open at the top, so that the hot gases generated `by the arc may pass oll' therethrough. In other cases, however, it will be found desirable to close the top of the struc- 1 ture by means of a cover of asbestos or other insulating refractory material.

The deionizing structure 1, of the form above described, may be supported on the stationary Contact 2 by an extension of the end plate 9, or it may beheld in the desired position by other means which will be readily apparent to those skilled in the circuit-breaker art. In any event, the end plates 9 should he extended downwardly and inwardly to form arcing horns to which the arcs drawn between- For example, it has been found that, with a slot $6 of an inch wide, and a distance 1 inch between the plates 9, about 1000 volts r. m. s. of 60 cycle alternating Voltage may be successfully interrupted.

If the slot width is made too small, the side walls may be overheated when it is attempted to interrupt the large currents. Therefore, the slot width and height should be proportioned in view of the current to be interrupted, and the distance between the end plates 9 should then be so related to the slot width as to suflice to interrupt voltage of the line in which the circuit interrupter is to be used.

To facilitate the design of slots, it may be said that a slot agg wide and 2 high has operated successfully with an arc current of 1000 amperes r. 1n. s.

It will be obvious that a sufficient number' and thickness of insulated sheets should be used between the iron laminations to withstand the stress of the line voltage if impressed between the end plates 9. The throughbolts 8 should, of course, be insulated from the laminations and from the end plates 9 by insulating tubes and collars capable of withstanding the stress of the line potential.

While the upper ends of the laminations are shown outwardly tapered to provide a structure in which the arc has a position of equilibrium at the narrow middle part of the slot, this is unnecessary in certain classes of service, and, therefore, the iron work may be arranged to close the slot completely at its upper end. In any ease, the insulating lining should cover the slot completely so that no iron is left exposed.

The broad idea of using a narrow slot between insulated side walls is being claimed, in a copending application Serial Number 208,686 of Joseph Slepiamiled July 27, 1927, the present application being directed primarily to the magnetic arrangement abovedescribed.

While l`I have described my deionizing structure as applied to circuit breakers employing separable contacts between which the arc is drawn, it will be evident that it may advantageously be applied to fuses which interrupt a circuit by melting or vaporizing the fusible member. It will also be evident that, while I have described this arrangel ment as applicable to alternating-current circuits, it may also serve for-the interruption of direct currents as well.

Many modilications of the structural embodiment which I have here described will be evident to those skilled in the art without departing from the principles which I have disclosed. I desire, therefore, that the language of the following claims shall be given its broadest reasonable interpretation and that they shall be limited only by their express terms and in view of the prior' art.

`I claim as my invention:

1. In combination with means to establish an arc, deionizing means comprising closely spaced walls of insulating material backed by a pair of members of magnetic material, having no connecting portions of magnetic material therebetween.

2. In combination with means for estab- 3. In combination with means to establish an arc, deionizing means comprising spaced walls of insulating material backed by a pair of members of magnetic material, conducting means forming arc terminal members to close in the separable contacts between said walls, except in the region adjacent to said first means, said magnetic members having an axis of symmetry substantially parallel to the arc path between said terminal members.

4. In combination with means to establish an arc, deionizing means comprising spaced walls of insulating material backed by members of magnetic material which diverge in the region of said first means to embrace it, and the space between said walls being closed by a pair of arc terminal members on two sides, except in the vicinity of said first' means.

5. In combination with a pair of separable electrical contact members, deionizing means comprising closely spaced walls of insulating material backed by a pair of magnetically isolated members of ma netic material.

6. In combination wit a pair of separable electrical contact members, deionizing means comprising spaced walls of insulating material backed by members of magnetic material diverging in the vicinity of said contact members to embrace them, said magnetic members being substantially symmetrical about an axis substantially parallel to the arc path.

7. In combination with a pair of. separable electrical contact members, deionizing means comprising spaced walls of insulating material backed by members of magnetic material completely s aced from each other by a gap of high re uctance, and conducting means forming arc horns to close in the space between said walls except near said contact members.

8. In combination with a air of separable electrical contact members, eionizing means comprising a pair of spaced walls of insulating material backed by magnetic material which diverges in the region of said Contact members to embrace them, and are horns to close in the space between said Walls, except in the region of said contact members.

9. In combination with a pair of separable contact members, arcing horns adjacent to said contact members, deionizing means comprising spaced walls of insulating material backed by members of magnetic material diverging in the vicinity of said contact members and having a gap of high reluctance between the entire areas thereof, and means comprising the said arcing horns to close in the space between said walls except in the region of said contact members.

10. In combination with an alternatingcurrent. source, means to establish an arc supplied thereby, deionizing means comprising spaced walls of insulating material backed by members of magnetic material completely spaced from each other by a gap of high reluctance, electrodes adapted to receive the termini of said arc disposed to close each end of the space between said walls, the r. m. s. value of the voltage of said source being not substantially greater than times the distance between said electrodes divided by the distance between said walls.

11. In combination with means to establish an arc, deionizing means comprising spaced walls of insulating material backed by a magnetic material, so shaped as to provide a. position of equilibrium for the arc between said walls.

12. In combination with a pair of separable contact members, arcing horns adjacent to said contact members, deionizing means comprising spaced walls of insulating material backed by magnetic material diverging on the side adjacent to said contact members and on the side opposite thereto, and means comprising the said arcing horns to close in the space between said walls except in the region of said contact members.

13. In combination with means to establish an arc, deionizing means comprising spaced walls of insulating material backed by a magnetic material, so shaped as to provide a position of equilibrium for the arc between said walls at a point such that the length of the arc is at least one sixtieth of the product of the distance in inches between said walls by the r. In. s. value of the voltage of the source supplying current to said arc.

In testimony whereof, I have hereunto subscribed my name this 24th day of January,

RURIC C. MASON. 

